Microtubules play a central role in cell motility, in the maintenance of cell architecture, and in the movement of a variety of intracellular organelles. Although the overall objective of this project is to understand how microtubules participate in secretion, the underlying assumption is that the basic mechanisms of microtubule assembly and function are similar for all cells. Hence, a general analysis of microtubule behavior in vivo and in vitro is directly relevant to understanding how microtubules work in secretion. Conversely, information about microtubule behavior in secretory cells should be applicable to other systems as well. Specific aims of the project include: 1. the in vivo reconstruction of a microtubule dependent motile system, 2. the development of immunologic techniques for clarifying the role of the high molecular weight microtubule associated proteins in microtubule function, 3. the development of immortal insulin secreting cell lines, 4, the clarification of regulation of microtubule assembly in cultured cells, 5. the purification of endogenous factors which effect colchicine bindng to tubulin, and 6. the identification and study of microtubular abnormalities in diabetes.